|
|
|
Volume 11, Number 6, Summer 1993
Oxygen Therapyby Barry Make, M.D.
Who needs oxygen? ...
Selecting the system ...
Oxygen conservers ... Long-term oxygen therapy is now widely accepted as the standard treatment for chronic hypoxia caused by chronic obstructive pulmonary disease or other disorders such as interstitial lung disease. Oxygen therapy has also become much more versatile in recent years, as several different types of oxygen delivery devices have become available. The diversity of these devices makes it easier for physicians to select a mode of oxygen therapy that suits the patient's lifestyle. Many patients require long-term oxygen therapy. The American Lung Association estimates that more than 800,000 Americans are maintained on long-term, chronic oxygen therapy. Oxygen therapy is a significant national health care expenditure; it is the most expensive non-surgical treatment reimbursed by Medicare. The typical monthly cost of oxygen therapy is $300. Patients with private insurance or Medicare coverage usually pay 20% of the cost, or about $60 a month. Because most patients on supplemental oxygen must receive it continuously, and in most cases for the rest of their lives, they may erroneously view oxygen therapy as a treatment of last resort. In reality, it is an important adjunct to other modes of treatment for chronic hypoxia.
Many primary care physicians are capable of identifying which patients need oxygen therapy, determining a patient's appropriate oxygen prescription, and establishing an oxygen therapy program. However, there are advantages to having these steps performed by oxygen therapy specialists. National Jewish Medical and Research Center operates a Center for Oxygen Therapy, which welcomes patient referrals.
Return to the table of contents Physicians should assess the need for oxygen therapy patients with chronic lung disease, especially those who complain of dyspnea and are not completely responsive to medical management. A general rule is that an analysis of resting blood gases is mandatory for patients with a forced expiratory volume (FEV1)of one liter or less despite receiving optimal medical treatment. At high altitudes, such as in the Rocky Mountain region, the minimum FEV1 that should trigger a blood gas analysis is 1.2 to 1.25 liters. Chronic hypoxia can be documented in patients who are already receiving optimal medical therapy by drawing an arterial blood specimen for analysis of arterial blood gases. The blood should be drawn from patients at rest, in the seated position. The patient is considered hypoxic and in need of supplemental oxygen if the arterial oxygen pressure (PaO2) at rest is at or below 59 mmHg or less if the patient also has a hematocrit of 55% or more, "p"pulmonale on an ECG, or peripheral edema that indicates right-sided heart failure. A normal PaO2 at rest does not rule out abnormally low oxygenation during exercise or sleep; oxygen saturation can be measured during these times using an oximeter. Return to the table of contents The companies that supply oxygen therapy may provide a patient with the least expensive system unless otherwise directed by the physician's prescription. It is therefore critical that a doctor be as specific as possible in defining the parameters of oxygen therapy. Of particular importance is specification of a supply system that provides the patient with the maximum degree of mobility that is consistent with the patient's lifestyle. A complete oxygen prescription must also specify the oxygen flow at rest, during activity, and during sleep. The appropriate oxygen dose during activity is determined by having the patient engage in these activities while measuring the patient's blood oxygen level with a fingertip oximeter. An adequate oxygen supply maintains an oxygen saturation of 90%. Other prescription parameters include the frequency of oxygen use each day, the duration of use, and the way by which the oxygen therapy company should monitor whether the patient is correctly using the therapy equipment. The least expensive and least portable device for oxygen therapy is an oxygen concentrator, which concentrates atmospheric oxygen and provides this as supplemental oxygen to the patient. These devices are usually powered electrically, and are outfitted with an oxygen tube that is, at most, 50 feet long. This design makes the concentrator suitable only for patients who are confined to home. In addition to their low cost, concentrators have the advantage of requiring the lowest number of maintenance visits. A monthly visit to check the operation of the concentrator is typical. Portable systems, which dispense oxygen from cylinders, are of two basic types based on whether the oxygen is stored as a liquid or gas. Gas cylinders are readily available and of moderate cost. Although more portable than a concentrator, the patient's mobility is still somewhat restricted by the bulkiness of these cylinders. These systems are feasible for patients who require a low oxygen flow.
Because they rely on smaller cylinders that are readily refilled at home from a
reservoir, liquid oxygen systems provide the greatest degree of portability and
versatility. Liquid oxygen systems are the most costly option, and are not
available to all patients, particularly those who live in rural areas. Liquid
oxygen is usually available in most large towns, and within a 50-60 mile radius
of most cities. Liquid oxygen cylinders are easier to fill from stationary
reservoirs than tanks that hold gas oxygen.
Return to the table of contents Oxygen delivery systems may be augmented with an oxygen conservation device, which allows a reduction in the oxygen flow rate while maintaining adequate oxygenation. Three types of oxygen conservation devices are available: reservoir devices, demand delivery devices, and transtracheal oxygen catheters. Reservoir devices store oxygen during the expiratory phase of ventilation, and deliver the stored oxygen during inspiration. These devices can achieve a 50-60% oxygen savings in patients with chronic obstructive pulmonary disease, and they are effective whether the patient is at rest or exercising. Although reservoir conservers are inexpensive and easy to use, patients often dislike them because they are more unsightly than standard nasal prongs. This may interfere with optimal patient compliance. Demand oxygen conservers provide oxygen only during inspiration, and save oxygen by shutting off flow during expiration. These units work by detecting negative pressure at the nose, at which time they trigger oxygen flow into the nasal cannula. Although several demand conservers are available, only four have been proven effective in rigorous studies. These are the Oxymatic, Companion Oxygen Saver, Pulsair, and Companion 550.
The SCOOP-1 catheter contains only an end port, and is suitable for low flow rates. The SCOOP-2 catheter has side ports in addition to the end port, and is suited to higher flow rates. The SCOOP-2 catheter requires daily removal and cleaning by the patient. The SCOOP-1 catheter can be cleaned in place, although it can also be removed for cleaning. Studies have documented that transtracheal catheters conserve oxygen and improve compliance with the oxygen prescription. In addition, transtracheal oxygen can provide important physiologic benefits by decreasing the patient-generated inspired volume and dead space. This effect results in reduced work of breathing for the patient. In addition, transtracheal oxygen may improve the patient's exercise capacity. The disadvantages of transtracheal delivery are the need for daily catheter cleaning, and complications from tracheal placement. One complication is infection, either in the form of cellulitis at the insertion site, or a lower respiratory tract infection. The most important complication during long-term use is development of mucus balls, which form around the catheter. These balls may become large enough to cause partial tracheal obstruction. Clinically significant mucus balls occur in 10-25% of patients. Despite such complications, patients usually elect to continue transtracheal oxygen because of the treatment's benefits.
Patient educationReturn to the table of contents All elements of oxygen therapy require thorough patient education and support if the treatment is to be successful. A physician should begin the educational process when long-term oxygen is initially prescribed, and should continue with help from the respiratory care practitioners who assist the patient with oxygen therapy at home. It is particularly important to address the patient's concerns and attitudes about oxygen therapy. Patients often react to the news that they require oxygen therapy with questions such as: "Am I that bad?", "Can't I just use it when I feel I have to?", "Will I ever be able to get off it?", and "I could never be seen in public with that on." The transition to routine oxygen therapy is difficult, particularly for patients who are not significantly short of breath and do not feel noticeably different when using oxygen. Physicians should stress the effect of oxygen therapy on quality of life, and avoid the mistake of emphasizing how oxygen therapy will help prolong a patient's life. Although this is a compelling medical rationale for oxygen therapy, patients may feel that they don't want to live longer if their life will be made miserable by the treatment. Instead, emphasize that oxygen therapy will help relieve shortness of breath and help improve performance. One approach that is often successful is a tangible demonstration of the benefits of oxygen therapy. Have the patient walk in a corridor or outside for a specific length of time, such as six minutes. Then have the patient walk in a corridor or outside for a specific length of time, such as six minutes. Then have the patient walk for the same time interval while on oxygen therapy. Compare the distances walked each time, and emphasize that oxygen therapy can significantly improve the patient's ability to perform routine activities.
The most effective way to educate patients about the use of oxygen delivery
equipment is a hands-on approach that centers on demonstrations with the
specific equipment that the patient will use. This places a lot of educational
responsibility in the hands of the therapists who help patients set up and use their equipment.
Return to the table of contents No clear evidence exists on how often a patient's oxygen therapy prescription should be reviewed. This question is now being addressed by a research project at National Jewish. Despite this uncertainty, patients clearly need reevaluation as their disease progresses. For the time being, our recommendation is to review the efficacy of oxygen therapy every six months, or whenever there is a significant change in the patient's clinical status. Return to the table of contents
Return to the table of contents Barry Make, M.D., F.A.C.P., F.C.C.P. Director of Pulmonary Rehabilitation, National Jewish; Associate Professor of Medicine, University of Colorado School of Medicine Philip Corsello, M.D., F.C.C.P. Senior Staff Physician, National Jewish; Clinical Associate Professor of Medicine, University of Colorado School of Medicine Gary Ferguson, M.D. Director of Emphysema Rehabilitation Program, National Jewish; Assistant Professor of Medicine, Division of Pulmonary Sciences, University of Colorado School of Medicine
|
|
National
Jewish Medical and Research Center 1400 Jackson Street Denver, CO 80206-2671 303-388-4461 - Lung Line® - 1-800-222-LUNG |
| The Medical Scientific Update, a publication of the Office of Professional Education at National Jewish, provides information to physicians about our clinical and research programs in allergic, respiratory, and immune system disorders. The Web edition of the Medical Scientific Update published by the Gerald Tucker Memorial Medical Library. |
|
| ©2006. National Jewish Medical and Research Center. | |
